Multi-chamber vacuum pump

ABSTRACT

A vacuum pump may be used to attach a prosthetic and/or orthotic device to a residual limb. The vacuum pump may be in line below a socket of a residual limb. The socket may be a portion of the prosthesis that accepts the residual limb. The vacuum pump may generate a vacuum condition between the prosthesis and the residual limb. Generally, a vacuum condition may be generated between a socket and the residual limb. The residual limb may be covered with a sock, elastomeric liner, or sheath covering the limb. The vacuum condition may positively attach the prosthesis to the residual limb without the need for straps, retaining pins, or suction type vacuum which do not use a vacuum pump.

TECHNICAL FIELD

The present disclosure relates generally to prosthetic systems andmethods, and relates particularly to systems and methods for generatinga vacuum condition that assists in connecting a prosthetic device to aresidual limb.

BACKGROUND

An amputee is a person who has lost part of an extremity or limb such asa leg or arm. The extremity of the limb left after amputation is termeda residual limb or a stump. Residual limbs come in various sizes andshapes depending on the person and the amputation. New amputations maybe slightly bulbous or cylindrical in shape. Older amputations may haveatrophied and may become more conical shape. A residual limb mayadditionally or alternatively be characterized by various individualproblems and configurations including the volume and shape of the stumpand possible scar, skin graft, bony prominence, uneven limb volume,neuroma, pain, edema or other soft tissue configurations. Prosthetic andorthotic devices may provide enhanced mobility and/or functionality toamputees but must be secured to a residual limb to do so. Keeping andmaintaining a strong connection between a residual limb and a prostheticor orthotic device is difficult.

There is, therefore, a need for improvements in how prosthetic andorthotic devices are connected to an maintain connection with theresidual limb of an amputee.

SUMMARY

A vacuum pump may be used to attach a prosthetic device to a residuallimb. The vacuum pump may be positioned in line and distal to a socketof the prosthetic device. The socket may be a portion of the prosthesisthat accepts the residual limb. The vacuum pump may generate a vacuumcondition that is applied in the socket to maintain a connection betweenthe prosthetic device and the residual limb. The residual limb may becovered with a sock, elastomeric liner, or sheath covering the limb. Thecovered residual limb may be inserted into socket of the prostheticdevice. The vacuum condition provided by the vacuum pump may positivelyattach the prosthesis to the residual limb using very low pressure andwithout the need for straps, retaining pins, or other types of suctiondevices that do not use a vacuum pump.

According to one aspect of the present disclosure, a vacuum pump for aprosthesis is described. The vacuum pump includes a housing having aninner wall. The vacuum pump also includes a piston having an outerdiameter and the piston is secured within the housing. A shaft having aninner surface is positioned between the inner wall of the housing andthe outer diameter of the piston. An upper fluid chamber is positionedbetween a top surface of the piston and the inner surface of the shaft.The upper chamber has a variable volume as the shaft moves axially inrelation to the piston and the housing. The upper chamber is fluidlyconnected to a socket of the prosthesis through a first valve and isfluidly connected to atmosphere through a second valve. A lower fluidchamber is positioned between a bottom surface of the piston and theinner surface of the shaft. The lower fluid chamber has a variablevolume as the shaft moves axially in relation to the piston and thehousing. The lower fluid chamber is fluidly connected to the socketthrough a third valve and is fluidly connected to atmosphere through afourth valve.

In some embodiments, the first valve and third valve may beindependently fluidly connectable to an evacuation volume. In someinstances, the evacuation volume may decrease as the vacuum pumpoperates, thereby causing a vacuum condition in the evacuation volume.The shaft may be axially movable to compress a volume of the upper fluidchamber while expanding a volume of the lower fluid chamber and viceversa. In some embodiments, compressing a volume of the upper fluidchamber may cause air to exhaust via the second valve into atmosphere.

In some instances, the piston may be an assembly comprising a firstpiece of the piston, wherein the first piece of the piston issubstantially cylindrically shaped. A second piece of the piston may bea flattened torus. The second piece of the piston and first piece of thepiston may form the piston assembly. In some embodiments, the firstpiece of the piston may incorporate a series of fluid channels fluidlyconnecting the upper chamber and the lower chamber to the socket.

In some instances, a compressible seal may be positioned around an outerdiameter of the piston. In some embodiments, the compressible seal mayfluidly separate the upper chamber from the lower chamber while enablingthe shaft to move axially in relation to the piston. In some instances,the valves are one-way valves allowing fluid flow in a single direction.The vacuum pump may also comprise a prosthetic leg, wherein theprosthetic leg comprises a prosthetic foot and a socket, with the socketbeing configured to accept a residual limb and the vacuum pump beingconfigured to evacuate fluid from the socket.

In another aspect of the disclosure, a vacuum pump for a prostheticdevice is provided which may comprise a housing having an inner wall, apiston having an outer diameter and being secured within the housing,and a shaft having an inner surface and being positioned between theinner wall of the housing and the outer diameter of the piston. An upperfluid chamber may be positioned between a top surface of the piston andthe inner surface of the shaft, wherein the upper fluid chamber may havea variable volume as the shaft moves axially in relation to the pistonand the housing. The upper fluid chamber may also be fluidly connectedto a first pair of one-way valves. A lower fluid chamber may bepositioned between a bottom surface of the piston and the inner surfaceof the shaft, wherein the lower fluid chamber may have a variable volumeas the shaft moves axially in relation to the piston and the housing.The lower fluid chamber may be fluidly connected to a second pair ofone-way valves.

In some arrangements, at least a first valve of the first and secondpair of one-way valves may be fluidly connected to a socket of theprosthetic device, and at least a second valve of the first and secondpair of one-way valves may be fluidly connected to atmosphere.Compressing a volume of the upper fluid chamber may cause air to exhaustvia the one of the first pair of one-way valves into atmosphere.

The pump may also comprise a compressible seal positioned around anouter diameter of the piston, wherein the compressible seal fluidlyseparates the upper fluid chamber from the lower fluid chamber whileenabling the shaft to move axially in relation to the piston.

Yet another aspect of the disclosure relates to a vacuum pump for aprosthetic device, wherein the vacuum pump comprises a shaft, a housing,a first fluid chamber, a second fluid chamber, and a third fluidchamber. Each of the first, second, and third fluid chambers may besealed and may have a variable volume upon movement of the shaftrelative to the housing. The first fluid chamber may be fluidlyconnected to a first pair of one-way valves, the second fluid chambermay be fluidly connected to a second pair of one-way valves, and thethird fluid chamber may be fluidly connected to a third pair of one-wayvalves.

At least one of the one-way valves may be shared by the first pair ofone-way valves and the second pair of one-way valves. The first andsecond fluid chambers may be arranged in series or in parallel.

Still another aspect of the disclosure relates to a vacuum pump for aprosthetic device that may comprise a housing having an inner wall, apiston having an outer diameter, a top surface, and a bottom surface,with the piston being held stationary relative to the housing, and ashaft having an inner surface and being positioned between the innerwall of the housing and the outer diameter of the piston. An upper fluidchamber may be positioned between the top surface of the piston and theinner surface of the shaft, wherein the upper fluid chamber may have avariable volume as the shaft moves axially in relation to the piston andthe housing and the upper fluid chamber may be in fluid communicationwith a first valve and a second valve. A lower fluid chamber may bepositioned between the bottom surface of the piston and the innersurface of the shaft, wherein the lower fluid chamber may have avariable volume as the shaft moves axially in relation to the piston andthe housing and the lower fluid chamber may be in fluid communicationwith a third valve and a fourth valve. A switch may be configured tocontrol the operation of the vacuum pump between a parallel vacuum pumpconfiguration and a series vacuum pump configuration, and at least oneof the first and third valves may be fluidly connected to the a socketof the prosthetic device and at least one of the second and forth valvemay be fluidly connected to atmosphere.

In some embodiments, when the vacuum pump is in the parallel vacuum pumpconfiguration, the first and third valves are both fluidly connected tothe socket and the second and fourth valves are fluidly connected toatmosphere. When the vacuum pump is in the series vacuum pumpconfiguration, the first valve may be fluidly connected to the socket,the second valve may be fluidly connected to the lower fluid chamber,the third valve may be fluidly connected to the lower fluid chamber, andthe fourth valve may be fluidly connected to atmosphere.

A further aspect of the present disclosure relates to a method ofoperating a vacuum pump for a prosthetic device. The method includesproviding a vacuum pump. The vacuum pump includes a housing having aninner wall, and a piston having an outer diameter and being securedwithin the housing. The vacuum pump includes a shaft having an innersurface. The shaft is positioned between the inner wall of the housingand the outer diameter of the piston. The vacuum pump includes an upperfluid chamber positioned between a top surface of the piston and theinner surface of the shaft. The upper chamber has a variable volume asthe shaft moves axially in relation to the piston and the housing. Theupper chamber is fluidly connected to a socket of the prosthesis througha first valve and fluidly connected to atmosphere through a secondvalve. A lower fluid chamber is positioned between a bottom surface ofthe piston and the inner surface of the shaft. The lower chamber has avariable volume as the shaft moves axially in relation to the piston andthe housing. The lower fluid chamber is fluidly connected to the socketthrough a third valve and fluidly connected to atmosphere through afourth valve. The method includes attaching the vacuum pump to thesocket. The socket is configured to receive a residual limb that has aliner mounted thereto. The method includes moving the shaft in a firstaxial direction relative to the piston thereby causing air to exhaustfrom the first chamber through the second valve and air to be drawn intothe second chamber through the third valve. The method further includesmoving the shaft in a second axial direction relative to the pistonthereby causing air to exhaust from the second chamber through thefourth valve and air to be drawn into the first chamber through thefirst valve.

In some embodiments, the method may include generating a vacuumcondition between the socket and the liner when air is drawn into thesecond chamber through the third valve.

In some instances, the method may include connecting the pump to aprosthetic foot and transferring load from the socket to the footthrough the pump.

In some instances, the method may include increasing a fluid volume ofthe second chamber as the shaft moves axially in the first direction.The method may include decreasing a fluid volume of the first chamber asthe shaft moves axially in the first direction. In some embodiments, themethod may include increasing a fluid volume of the second chamber asthe shaft moves axially in the first direction. The method may includedecreasing a fluid volume of the first chamber as the shaft movesaxially in the first direction.

Another aspect of the disclosure relates to a vacuum pump switch for aprosthetic device, wherein the switch may comprise a housing, an inletpassage formed in the housing and configured to provide fluidcommunication with an evacuation volume, a first fluid inlet valvepassage configured to provide fluid communication to a first chamber ofa vacuum pump, a second fluid inlet valve passage configured to providefluid communication to a second chamber of the vacuum pump, a firstfluid outlet valve passage configured to provide fluid communication tothe first chamber, a second fluid outlet valve passage configured toprovide fluid communication to the second chamber, an outlet passageformed in the housing, and a switch. The switch may be operable betweena first position and a second position. In the first position, fluidflow from the inlet passage may be provided simultaneously to the firstand second fluid inlet valve passages and flow to the outlet passage maybe provided simultaneously from the first and second fluid outlet valvepassages. In the second position, fluid flow from the inlet passage maybe provided to the first fluid inlet valve passage, fluid flow to thesecond fluid inlet valve passage may be provided from the first fluidoutlet valve passage, and fluid flow to the outlet passage may beprovided from the second fluid outlet valve passage.

In some arrangements, the vacuum pump switch may also comprise a vacuumpump comprising a housing and a piston, with the housing comprising asealed volume and with the piston dividing the sealed volume into thefirst chamber and the second chamber.

The foregoing has outlined rather broadly the features and technicaladvantages of examples according to this disclosure so that thefollowing detailed description may be better understood. Additionalfeatures and advantages will be described below. The conception andspecific examples disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present disclosure. Such equivalent constructions do notdepart from the scope of the appended claims. Characteristics of theconcepts disclosed herein-including their organization and method ofoperation-together with associated advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. Each of the figures is provided for the purpose ofillustration and description only, and not as a definition of the limitsof the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings and figures illustrate a number of exemplaryembodiments and are part of the specification. Together with the presentdescription, these drawings demonstrate and explain various principlesof this disclosure. A further understanding of the nature and advantagesof the present invention may be realized by reference to the followingdrawings. In the appended figures, similar components or features mayhave the same reference label.

FIG. 1 illustrates an example prosthetic device coupled to a residuallimb using a vacuum pump in accordance with the present disclosure.

FIG. 2A is a schematic representation of a parallel multi-chamber vacuumpump.

FIG. 2B is a schematic representation of a series multi-chamber vacuumpump.

FIG. 3A is a side view of an example vacuum pump in accordance with thepresent disclosure.

FIG. 3B is a perspective view of the vacuum pump shown in FIG. 3A with acutaway side portion showing internal components.

FIG. 3C is a cross-sectional side view of the vacuum pump shown in FIG.3A taken along cross-section indicators 3C-3C shown in FIG. 3B.

FIG. 3D is a cross-sectional top view of the vacuum pump shown in FIG.3A taken along cross-section indicators 3D-3D shown in FIG. 3A.

FIG. 4 is an exploded view of the vacuum pump shown in FIG. 3A.

FIG. 5A is an perspective view of an example piston for use in thevacuum pumps disclosed herein.

FIG. 5B is a top view of the piston shown in FIG. 5A.

FIG. 5C is a cross-sectional view of the piston shown in FIG. 5A takenalong cross-section indicators 5C-5C in FIG. 5B.

FIG. 5D is a cross-sectional view of the piston shown in FIG. 5A takenalong cross-section indicators 5D-5D in FIG. 5B.

FIG. 5E is a cross-sectional side view of the piston shown in FIG. 5Ataken along cross-section indicators 5E-5E in FIG. 5B.

FIG. 6 is a cross-sectional view of an example parallel vacuum pump in afirst operational state in accordance with the present disclosure.

FIG. 7 is a cross-sectional view of the parallel vacuum pump shown inFIG. 6 in a second operational state.

FIG. 8 is a cross-sectional view of the parallel vacuum pump shown inFIG. 6 in a third operational state.

FIG. 9 is a cross-sectional view of an example series vacuum pump inaccordance with the present disclosure.

FIG. 10 is a cross-sectional view of an example combination parallel andseries vacuum pump in accordance with the present disclosure.

FIG. 11 is a cross-sectional view of an example three stage seriesvacuum pump in accordance with the present disclosure.

FIG. 12A is a schematic representation of a mode switching multi-chambervacuum pump in parallel mode in accordance with the present disclosure.

FIG. 12B schematic representation of a mode switching multi-chambervacuum pump in series mode in accordance with the present disclosure.

FIG. 13A is an perspective view of an example switching vacuum pump inaccordance with the present disclosure.

FIG. 13B is a side view of the switching vacuum pump shown in FIG. 13A.

FIG. 13C is a partial cross-sectional view of the switching vacuum pumpshown in FIG. 13B taken along cross-section indicators 13C-13C.

FIG. 14 is a partial exploded view of the vacuum pump shown in FIG. 13A.

FIG. 15 is a side view of an example switch for use in a vacuum pump inaccordance with the present disclosure.

FIG. 16A is a cross-sectional view of the switch shown in FIG. 15 takenalong cross-section indicators 16A-16A, the switch being arranged in aparallel mode.

FIG. 16B is a cross-sectional view of the switch shown in FIG. 15 takenalong cross-section indicators 16A-16A, the switch being arranged in aseries mode.

FIG. 16C is a cross-sectional side view of the switch shown in FIG. 15taken along cross-section indicators 16C-16C, the switch being arrangedin a series mode.

FIG. 17A is a cross-sectional view of an example switch for use in avacuum pump in accordance with the present disclosure, the switch beingarranged in a parallel mode.

FIG. 17B is a cross-sectional view of the switch shown in FIG. 17Aarranged in a series mode.

While the embodiments described herein are susceptible to variousmodifications and alternative forms, specific embodiments have beenshown by way of example in the drawings and will be described in detailherein. However, the exemplary embodiments described herein are notintended to be limited to the particular forms disclosed. Rather, theinstant disclosure covers all modifications, equivalents, andalternatives falling within the scope of the appended claims.

DETAILED DESCRIPTION

Vacuum suspension may be used to couple a prosthetic device (alsoreferred to as a prosthesis) to a residual limb. When a limb interfaceis subject to high levels of vacuum, retention may occur with nosignificant movement between the residual limb and the prostheticdevice. The vacuum condition may additionally provide residual limbvolume management and increased proprioception. Vacuum suspension mayadditionally improve circulation and may increase a rate at which awound heals on the residual limb.

Vacuum level is the difference in air pressure between an evacuatedvolume and a neighboring volume. The neighboring volume in a prostheticapplication may be atmospheric pressure. Initially, a socket of theprosthetic device does not have adequate vacuum suspension to realizeits benefits. To initiate vacuum suspension, a vacuum pump may be cycledafter a prosthetic device is attached to a residual limb. The cycling ofthe vacuum pump may generate a vacuum suspension which may enable thebenefits aforementioned. Cycling a vacuum pump, as mentioned herein, isrunning a vacuum cycle several times. Additional layers of material maybe located between the socket and liner to facilitate fit, comfort,and/or the evacuation of air.

During use, the vacuum volume may leak and the vacuum condition maybleed off if the vacuum pump is not cycled. This may occur duringperiods of inactivity of the pump. If the pump is a mechanical pump,this may equate to inactivity of a user. Prior to a person then using aprosthetic attached with a vacuum interface, an adequate vacuumsuspension condition may need to be achieved. Quickly achieving thevacuum suspension may enable an amputee to become mobile more quickly.

FIG. 1 is an example use of a prosthesis 100 with a vacuum pump 102. Theprosthesis 100 may attach to a residual limb 104. The residual limb 104may fit into a liner or sock (not shown) (or the liner or sock may bedonned on or mounted to the residual limb 104). The residual limb 104with liner mounted thereto may then be inserted into a socket 108. Insome embodiments, additional layers of material may be located betweenthe socket and liner to facilitate fit, comfort, and/or the evacuationof air between the socket and liner. The socket 108 may be fluidlyconnected to the vacuum pump 102. The socket 108 may be rigidly coupledto other components of the prosthesis, such as prosthetic 110. Theprosthetic 110 may include a prosthetic shaft 112 and a prosthetic foot114.

The vacuum pump 102 may be an electrical or mechanical pump. Amechanical pump, as will be discussed, is cycled mechanically by theuser's weight during use to generate a vacuum pressure condition (alsoreferred to as a vacuum force or a vacuum condition). An electrical pumprequires a power source (not shown) to energize the pump and create avacuum. The power source may comprise a battery. The battery may bereplaceable and/or rechargeable. In some embodiments, use of theprosthesis 100 may generate a charge for the power source.

As shown in FIGS. 2A and 2B, the vacuum pump 102 may be a parallelvacuum pump 200 (see FIG. 2A) or a series vacuum pump 202 (see FIG. 2B).A parallel vacuum pump 200 includes two or more pumping chambers 208,210 and is configured to draw air out of a single volume to be evacuated(e.g., the socket 108 or a chamber that is in fluid communication withsocket 108). A series vacuum pump 202 includes a pumping chamber 230that is connected to the volume to be evacuated and exhausts to a secondchamber 232.

As shown in FIG. 2A, a parallel vacuum pump 200 is fluidly connected toan evacuation volume 204. The parallel vacuum pump 200 includes closed,sealed volume 206 comprising a first chamber 208 and a second chamber210. The first chamber 208 and second chamber 210 are fluidly connectedto the evacuation volume 204 via one or more intake passages 212. Apiston 214 moves within the sealed volume 206 and defines in part thefirst and second chambers 208, 210 within the sealed volume 206. Thepiston 214 may define a wall, that, in some embodiments, moves axiallyin the direction A-B relative to other components of the parallel vacuumpump 200. The parallel vacuum pump 200 may exhaust a fluid (e.g., air)from the evacuation volume 204 faster than (e.g., two times faster than)a single chamber vacuum pump.

As the piston 214 travels toward a bottom 216 of the sealed volume 206,the piston 214 causes the second chamber 210 to decrease in volume. Asthe piston 214 moves and the second chamber 210 decreases, the fluid inthe second chamber 210 exhausts to atmosphere via one or more exhaustpassages 218. At the same time, a volume of the first chamber 208increases. As the volume of the first chamber 208 increases, it pullsfluid (e.g., air) from the evacuation volume 204 via the one or moreintake passages 212. As the piston 214 continues to cycle and movetoward a top 220 of the parallel vacuum pump 200, the process switchesfor the first and second chambers 208, 210. The first chamber 208reduces in volume and exhausts a fluid via the one or more exhaustpassages 218. The second chamber 210 increases in volume and pulls afluid from the evacuation volume 204 via the one or more intake passages212. As the piston 214 continues to cycle, fluid continues to be pulledfrom the evacuation volume 204 thereby creating a vacuum condition inthe evacuation volume 204.

FIG. 2B displays an schematic of the series vacuum pump 202. The seriesvacuum pump 202 may comprise a closed, sealed volume 222, which may befluidly connected to an evacuation volume 224 via one or more intakepassages 226. A piston 228 may separate the sealed volume 222 into twochambers; a first chamber 230 and a second chamber 232. The one or moreintake passages 226 fluidly connects the evacuation volume 224 to thefirst chamber 230 of the series vacuum pump 202.

As the piston 228 moves towards a bottom 234 of the series vacuum pump202, the first chamber 230 may pull a fluid from the evacuation volume224 via the one or more intake passages 226. At the same time, a volumeof the second chamber 232 reduces. As the volume of the second chamber232 reduces, the fluid in the second chamber 232 exits the chamber 232via one or more exhaust passages 236. The one or more exhaust passages236 fluidly connects the second chamber 232 to either a third chamber(not shown) or atmosphere. As the piston 228 reciprocates and movestoward a top 238 of the series vacuum pump 202, the volume of the firstchamber 230 is reduced and the volume of the second chamber 232 isincreased. This causes the fluid in the first chamber 230 to exhaust andenter the second chamber 232 via connection passage 240.

This process then continues and the piston 228 reciprocates back towardthe bottom 234 of the series vacuum pump 202. This process creates avacuum condition that may result in a higher differential pressure, orincreased vacuum, that may be applied to a space between the residuallimb/liner and the socket.

FIGS. 3A-4 show views of an example vacuum pump 300 according to thepresent disclosure. FIG. 3A is a side view of a vacuum pump 300connected to a socket 301, FIG. 3B is a perspective view of the vacuumpump 300, FIG. 3C is a side section view of the vacuum pump 300 andsocket 301 taken through section lines 3C-3C in FIG. 3B, FIG. 3D is atop section view of the vacuum pump 300 taken through section lines3D-3D in FIG. 3A, and FIG. 4 is an exploded view of the vacuum pump 300.The vacuum pump 300 may be a parallel pump.

The vacuum pump 300 in FIG. 3C comprises a housing 302 and a shaft 304.The shaft 304 may move in relation to the housing 302. A cap 306 may becoupled to the housing 302. The cap 306 may alternatively be referred toas a lamination plate because it may be laminated to a limb socket 301.The housing 302 and cap 302 may be connected to each other using athreaded member 308. The cap 306 may threadably engage the threadedmember 308 to couple to the housing 302. A lip 309 at the top of thehousing 302 may keep the housing 302 from sliding out of the threadedmember 308. The housing 302 and cap 306 may alternatively be clampedtogether via mating threads, fastened together, adhered together, orotherwise coupled. Teeth 400, 402 may be positioned on the housing 302and cap 306, respectively, to help prevent the housing 302 from rotatingrelative to the cap 306 once the threaded member 308 is tightenedagainst the threads of the cap 306. See also FIG. 4 and relateddescriptions below.

The radial outer surface of the cap 306 may be laminated or otherwiseaffixed and attached to a limb socket 301 within which a limb liner 305may be positioned. Thus, the cap 306 may be formed integrally with thesocket 301. An evacuation volume 307 may be formed between the outersurface of the limb liner 305 and the inner surface of the socket 301.The cap 306 may additionally comprise an air passage 310 in fluidcommunication with the evacuation volume 307. The evacuation volume 307may be a volume from which air is drawn by the pump 300, such asevacuation volume 204.

A first bearing 314 and a second bearing 316 may provide a smooth,sliding interface between the housing 302 and the shaft 304. The firstbearing 314 and second bearing 316 may provide support between the shaft304 and housing 302 as the shaft 304 and the housing 302 move inrelation to each other. The bearings 314, 316 may also maintain aworking distance between an inner wall 318 of the housing 302 and anouter wall 320 of the shaft 304. A bottom seal 303 may keep out dirt andother contaminants from entering the interface between the housing 302and shaft 304.

The shaft 304 may comprise a multi-piece assembly. See FIGS. 3C and 4.For example, the shaft 304 may be an assembly comprising a body 322, atop cap 324, and a bottom cap 326. The bottom cap 326 may be coupled toan internal wall 328 of the body 322. The bottom cap 326 may betight-fit, press-fit, screwed, adhered, or otherwise coupled to the body322. In some embodiments, the bottom cap 326 may rest on a lip 330 onthe internal wall 328 of the body 322. The top cap 324 is coupled to atop of the body 322 of the shaft 304. The top cap 324, bottom cap 326,and body 322 may form a sealed volume 332. The sealed volume 332 may besimilar to the sealed volume 206 of the parallel pump 200.

A piston 334 may be situated in the sealed volume 332 and may separatethe sealed volume 332 into two evacuation chambers 336, 338. The piston334 may be movable relative to the sealed volume 332 and may fluidlyseparate the sealed volume 332 into a first evacuation chamber 336 abovethe piston 334 and a second evacuation chamber 338 below the piston 334.A compressible seal 340 may be located on an outer diameter 342 of thepiston 334 that may fluidly separate the first evacuation chamber 336and the second evacuation chamber 338 while enabling the piston 334 toreciprocate relative to the shaft 304 within the sealed volume 332.

The piston 334 may engage and contact the underside of the cap 306. Insome embodiments, the piston 334 may be attached or affixed to the cap306. For example, the piston 334 may be threadably engaged with, adheredto, or forced against the cap 306 at a top portion 344 of the piston334. The top portion 344 of the piston 334 may receive a cylindricalstem 346 of the cap 306 within a hollow portion 348 at the top portion344. An upper compressible seal 349 and lower compressible seal 347 maymaintain the sealed volume 332 while enabling the top portion 344 of thepiston 334 to mate with the cylindrical stem 346 of the cap 306 and passthrough and move relative to the top cap 324.

A bottom portion 350 of the piston 334 may pass through an opening 352in the bottom cap 326. The opening 352 may incorporate a compressibleseal 354, which may maintain the sealed volume 332 while enabling thebottom portion 350 of the piston 334 to pass through and move relativeto the opening 352. The bottom portion 350 of the piston 334 may contactand engage a compressible cylinder 356. The compressible cylinder 356may be a spring element and may comprise a resilient rod, spring coil,or similar elastically longitudinally compressible member. Thecompressible cylinder 356 may be fairly rigid, but may act as a springor dampening feature for the pump 300. The compressible cylinder 356 mayhave a spring rate within a range of about 10 N/mm to about 350 N/mm. Abottom 358 of the compressible cylinder 356 may contact or be coupled toa bottom cup 360 on the bottom cap 326.

The bottom cup 360 may support the compressible cylinder 356 and allowadjustment of the preload applied to the compressible cylinder 356. Aprosthetic pyramid connector may attach to the distal end of the shaft332 through the opening 362 and be secured using fasteners 363.Alternatively, the distal end of the shaft may be configured to clamp a30 mm or 34 mm tube (not shown). Thus, the prosthetic shaft and thevacuum pump 300 may be easily separable. For example, a user may utilizedifferent prosthesis components depending on, for example, the type orlevel of activity the user is engaged in. Alternatively, ease ofseparation may enable ease of maintenance and care for the vacuum pump300. Removal of the prosthetic shaft from opening 362 may also allow theuser to access the bottom cup 360 to remove, adjust, or service thecompressible cylinder 356.

The piston 334, housing 302, cap 306, and socket 301 may be stationaryrelative to each other and may move in unison/as an assembly relative tothe shaft 304 and the top and bottom caps 324, 326. As the piston 334moves relative to the sealed volume 332, the respective volumes of thefirst evacuation chamber 336 and the second evacuation chamber 338 mayvary. As the piston 334 moves in a direction A relative to the sealedvolume 332, the volume of the first evacuation chamber 336 may bereduced and the volume of the second evacuation chamber 336 may beincreased. As the piston 334 reciprocates and moves in a direction Brelative to the sealed volume 332, the volumes of the first evacuationchamber 336 and second evacuation chamber 338 again change. The volumeof the first evacuation chamber 336 may increase and the volume of thesecond evacuation chamber 338 may decrease. In one embodiment, thepiston 334 may be powered by an electrical motor (not shown). In anotherembodiment, if the prosthesis is a prosthetic leg, the piston 334 maymove down in the direction B relative to the sealed volume 332 when aperson puts weight on the prosthetic shaft or socket 301 since theweight applies a force to the shaft 304 that drives the shaft upward indirection A relative to the housing 302 and piston 334. When the persontakes a step and the weight is released, the piston 334 may move upwardin the direction A relative to the sealed volume 332 as the shaft 304moves downward in direction B relative to the housing 302.

Whether a vacuum pump of the present disclosure operates as a parallelvacuum pump or a series vacuum pump depends upon various fluid passagesand connections in the vacuum pump and the socket or evacuation volume.In FIGS. 3A-5D, the vacuum pump 300 is a parallel pump, meaning both thefirst and second evacuation chambers 336, 338 intake fluid from theevacuation volume 307. Each evacuation chamber 336, 338 may be suppliedwith air using one-way valves. The one-way valves may enable fluid toflow in a single direction through the valve. Separate one-way valvesmay permit flow out of the evacuation chambers 336, 338 and into theatmosphere surrounding the vacuum pump 300.

FIGS. 3C and 5B-5E illustrate air passages and chambers used to evacuatethe evacuation volume 307. Various views of the same piston 334 areshown in FIGS. 3C and 5A-5E. A first vertical intake passage 364 fluidlyconnects the evacuation volume 307 with the inside of the piston 334through hollow portion 348. The first vertical intake passage 364 islinked to a first horizontal intake passage 365 and a second horizontalintake passage 366. See FIG. 5D. The first and second horizontal intakepassages 365, 366 may have a first and second one-way intake valve 367,368, respectively. The first and second one-way intake valves 367, 368are one-way valves that enable fluid to flow only from the evacuationvolume 307 into the first and second evacuation chambers 336, 338,respectively. The first evacuation chamber 336 pulls fluid from theevacuation volume 307 via the first horizontal intake passage 365 as thepiston 334 travels downward in the direction B relative to the sealedvolume 332. The second evacuation chamber 338 pulls fluid from theevacuation volume 307 via the second horizontal intake passage 366 asthe piston 334 travels upward in the direction A relative to the sealedvolume 332. The piston 334 has air openings 369, 370, with one airopening 369 opening to the first evacuation chamber 336 and one airopening 370 opening to the second evacuation chamber 338. Air may passthrough the air openings 369, 370 to enter the first and secondevacuation chambers 336, 338 through the first and second one-way intakevalves 367, 368, as shown by the dashed-line flow paths in FIG. 5D.

Air in the first and second evacuation chambers 336, 338 may exit bypassing through the air openings in the piston 334. As the piston 334reciprocates in the sealed volume 332, air in the first evacuationchamber 336 may pass through air opening 369 in the top of the piston334 (see FIG. 5C), through a first one-way exhaust valve 372, through afirst horizontal exhaust passage 373, and to a vertical exhaust passage374 (see FIGS. 3C and 5E). Likewise, reciprocation of the piston 334 inthe sealed volume 332 in the opposite direction may cause air in thesecond evacuation chamber 338 to pass through air opening 370 in thebottom of the piston 334 (see FIG. 5C), through a second one-way exhaustvalve 376, through a second horizontal exhaust passage 377, and to thevertical exhaust passage 374 (see FIGS. 3C and 5E).

Air in the vertical exhaust passage 374 may escape into atmosphere bypassing through bottom portion 350 of the piston 334 between its innersurface and the compressible cylinder 356, then out of a vent opening378 in the bottom cap 326 and through the bottom opening 362 of thevacuum pump 300. See FIG. 3C. Accordingly, air may be pumped from theevacuation volume 307 through the vacuum pump 300 as the piston 334moves within the sealed volume 332. Air from the evacuation volume 307is vented to atmosphere during each pump cycle, which may correspond toeach step on the prosthesis to which the vacuum pump 300 is attached.Accordingly, walking on the prosthesis may continuously evacuate airfrom the evacuation volume 307, thereby preserving a low pressurecondition within the evacuation volume 307 and maintaining connectionbetween the socket 301 and the liner 305.

The compressible cylinder 356 or spring element may be used to bias thepiston 334 and to absorb shock as the vacuum pump 300 is used. Forexample, the compressible cylinder 356 may be configured to apply aforce to the bottom of the piston 334 in direction A as the compressiblecylinder 356 is compressed. The compressible cylinder 356 maysimultaneously apply a downward force against the bottom cup 360 thatbiases the piston 334 to be at the top of the sealed volume 332 withinthe shaft 304 when the pump 300 is not loaded. Thus, the section view ofFIG. 3C shows the piston 334 at a mid-stroke position relative to itsrest position within the sealed volume 332. At rest, the firstevacuation chamber 336 has its minimum (e.g., nearly zero) volume due tothe piston 334 being positioned vertically high up and in contact withthe bottom surface of top cap 324, and the second evacuation chamber 338has its maximum volume. At full stroke, the first evacuation chamber 336has its maximum volume, and the second evacuation chamber 338 has itsminimum volume due to the piston 334 being near the bottom of the sealedvolume 332 and near the top surface of the bottom cap 326. In someembodiments, the piston 334 does not come into contact the bottom cap326 since doing so would cause impact forces to be transferred to theuser's limb. Adjustment the preload of the compressible cylinder 356using the bottom cup 360 and/or selecting a compressible cylinder 356with an appropriate spring rate may prevent contact from occurring.

FIG. 3D is a top section view taken through section lines 3D-3D in FIG.3A. FIGS. 3B-3D and 4 illustrate a resilient rotation restrictionassembly that may be used in the vacuum pump 300. The rotationrestriction assembly may comprise a plurality of rigid blocks 380positioned on the inner wall 318 of the housing 302, a plurality ofrigid blocks 382 positioned on the outer wall 320 of the shaft 304, anda plurality of resilient blocks 384 positioned between the internalsurface of the housing 302 and the external surface of the shaft 304.See FIGS. 3B and 3D. The rigid blocks 380, 382 may be securely affixedto their respective walls 318, 320. The rigid blocks 380, 382 may becircumferentially spaced around the walls 318, 320 and may, uponassembly of the pump 300 have substantially equal longitudinal positionswithin the pump 300. As shown in FIG. 3D, the rigid blocks 380 on theinner wall 318 may be positioned about 180 degrees apart from each otherrelative to a longitudinal axis of the housing 302, and the rigid blocks382 on the outer wall 320 may be positioned about 180 degrees apart fromeach other relative to a longitudinal axis of the shaft 304.

Each of the plurality of resilient blocks 384 may be positioned betweenthe walls 318, 320 without being attached thereto. Upon assembly of thevacuum pump 300, the resilient blocks 384 may be positionedcircumferentially between the rigid blocks 380, 382. See FIGS. 3B and3D. Accordingly, at least one resilient block 384 may be positionedbetween each adjacent pair of rigid blocks 380, 382. Each of theresilient blocks 384 may comprise at least one chamfer 386. The chamfer386 may help guide the rigid blocks 380, 382 to be positioned betweenthe resilient blocks 384 as the vacuum pump 300 is assembled.

During use of the vacuum pump 300, the prosthetic shaft 112 may apply atorque to the shaft 304 (or housing 302) that urges the shaft 304 torotate around its longitudinal axis relative to the housing 302. A smallamount of relative rotation between the shaft 304 and the housing 302may be desirable for user comfort, but large angular displacementbetween the shaft 304 and housing 302 may cause misalignment of theprosthetic. Accordingly, the resilient rotation assembly may be usedwith the vacuum pump 300 to address these concerns.

When a torque is applied to the shaft 304, the shaft 304 may be urged torotate within the housing 302. This may also cause the rigid blocks 382on the outer wall 320 to rotate around the longitudinal axis of theshaft 304. Rotation of the rigid blocks 382 urges them circumferentiallytoward rigid blocks 380 on the inner wall 318 of the housing 302. Therigid blocks 380, 382 accordingly apply compressive forces to theresilient blocks 384 that are positioned in the path of rotation of therigid blocks 382. The rigid blocks 380, 382 may comprise a rigidmaterial (e.g., a metal), and the resilient blocks 384 may comprise acomparatively more resilient material (e.g., a rubber or resilientpolymer). Accordingly, the compressive forces on the resilient blocks384 may cause the resilient blocks 384 to deform and compress betweenthe rigid blocks 380, 382. The compressibility of the resilient blocks384 may allow a degree of relative rotation between the housing 302 andshaft 304 but may also limit the amount of relative rotation betweenthose parts. In some embodiments, about 7 degrees of rotation may beallowed by elastic compression of the resilient blocks 384 during normalwalking gait. When subjected to more extreme torsional loads, forexample when a user is golfing, about 10 degrees to about 40 degrees ofrotation may be allowed by the elastic compression. When the torque onthe shaft 304 (or housing 302) is released, the resilient blocks 384 mayresiliently apply forces to the rigid blocks 380, 382 that cause therigid blocks 380, 382 to circumferentially move back to their restpositions. Thus, the resilient blocks 384 automatically realign the limbafter rotational deflection between the shaft 304 and housing 302.

FIG. 4 is an exploded view of the vacuum pump 300. The vacuum pump 300includes subassemblies of the housing 302 and the shaft 304. The vacuumpump 300 may additionally and/or alternatively include assemblies and/orcomponents not disclosed herein.

FIG. 4 shows a plurality of housing teeth 400 positionedcircumferentially around the top of the housing 302. The housing teeth400 may engage teeth 402 positioned around the bottom surface of the cap306. See FIG. 3C. Thus, when the vacuum pump 300 is attached to thesocket 301 (and cap 306), the teeth 400, 402 may engage each other toprevent rotation between the housing 302 and the socket 301. Bypreventing rotation between the housing 302 and the socket 301, thethreaded member 308 may be threaded and tightened into place against thethreads of the cap 306 more easily and without slippage of the housing302 relative to the socket 301. Furthermore, the teeth 400, 402 ensurethat the housing 302 and socket 301 remain in place relative to eachother, even when torque is applied to the socket 301 or housing 302 thatwould urge one of them to rotate relative to each other around theircommon longitudinal axis. Torque applied to the housing 302 thereforewould not loosen the connection between the housing 302 and the socket301 since they are held together by the threaded member 308.

The plurality of teeth 400, 402 also allow the user to select aplurality of different predetermined relative angular positions for thehousing 302 relative to the socket 301 when the two are joined by thethreaded member 308. This capability would not be possible if thehousing 302 was directly threaded to the cap 306 since threads on thehousing 302 would need to be rotated to be tightened against the cap306, and the final rotated position of the housing 302 relative to thecap 306 would not be easily predetermined or set by the user due to thethreads.

FIG. 5A is a perspective view of the piston 334 of the vacuum pump 300.The piston 334 may comprise a two-piece assembly that incorporates oneor more fluid passages. FIG. 5B is a top down view of the piston 334.FIG. 5C is a cross-sectional view of the piston 334 along section lines5C-5C in FIG. 5B. FIG. 5D is a cross-sectional view of the piston 334along section lines 5D-5D in FIG. 5B. FIG. 5E side section view of thepiston 334 taken through section lines 5E-5E in FIG. 5B.

As shown in FIGS. 5C and 5D, the piston 334 may comprise a two-pieceassembly including an inner piece 500 and an outer piece 502. The innerpiece 500 may contain various passages for transferring fluid, asdescribed above. The inner piece 500 may comprise multiple cylindricalsections. For example, the inner piece 500 may include an upper section504, a middle section 506, and a lower section 508. The upper section504 has the smallest cylindrical diameter and connects to the cap 306.The middle section 506 has a larger diameter than the upper section 504and interfaces with the outer piece 502. The lower section 508 has asmaller diameter than the middle section 506 but a larger diameter thanthe upper section 504. The lower section 508 contacts the compressiblecylinder 356. The size of diameters and correlation between the sizes ofdiameters may vary. For examples, the diameters may be greater than,smaller than, or equal to other diameters. In some instances, there maybe greater or fewer sections of the inner piece 500.

In this embodiment, the upper section 504 may comprise the hollowportion 348. The lower section 508 may include a lower cylindrical void514, within which the piston 334 may receive the compressible cylinder356. See FIG. 3C. The compressible cylinder 356 may apply a force to thelower cylindrical void 514 to bias the piston 334 into contact with thecap 306.

The outer piece 502 may be a flattened torus. The outer piece 502 may bepress-fit onto the inner piece 500. The flattened torus mayalternatively be adhered or otherwise fastened to the inner piece 500.In some embodiments, an outer diameter 520 of the outer piece 502 mayincorporate a substantially rectangular groove 522. The groove 522 mayincorporate a compressible seal. The compressible seal may fluidlyseparate a first chamber and a second chamber of a seal volume in avacuum pump.

FIG. 6 is an alternative embodiment of a parallel vacuum pump 600. Thealternative embodiment may incorporate a shaft 602 and a housing 604.The parallel vacuum pump 600 may incorporate similar features of thevacuum pump 300 described with reference to FIGS. 3A-3C. For example, apiston 606 may be located within a sealed volume formed within the shaft602.

The sealed volume may be formed by the housing 604, a top cap 610, and abottom cap 612. The piston 606 may separate the sealed volume into afirst chamber 614 and a second chamber 616. In this embodiment, thepiston 606 may be a one-piece piston that incorporates one or moreintake valves. For example, the piston 606 may include a first intakepassage 618 that fluidly connects the first chamber 614 to an evacuationvolume (e.g., evacuation volume 204, 224). The first intake passage 618may include a first intake valve 620 that may be a one-way fluid valveenabling fluid flow in a single direction. The piston 606 mayadditionally include a second intake passage 622, which may fluidlyconnect the second chamber 616 to the evacuation volume. The secondintake passage 622 may include a second intake valve 624. The secondintake valve 624 may be a one-way valve enabling fluid flow in a singledirection.

The piston 606 is shown in a mid-stroke position. As shown, the piston606 is centrally located within the sealed volume. This situation mayarise as the piston 606 cycles during use. A spring member 656 mayotherwise bias the piston 606 and top cap 610 together. As shown, thefirst chamber 614 and the second chamber 616 have substantially similarvolumes. However, as the piston 606 reciprocates within the sealedvolume, the respective volumes of the first and second chambers 616, 618will vary.

A first exhaust passage 626 fluidly couples the first chamber 614 toatmosphere. The first exhaust passage 626 may enable fluid to exit thefirst chamber 614. A first exhaust valve 628 may be located within thefirst exhaust passage 626. The first exhaust valve 628 may be a one-wayvalve enabling fluid flow in a single direction, namely a direction awayfrom the first chamber 614.

A second exhaust passage 630 fluidly couples the second chamber 616 toatmosphere. The second exhaust passage 630 may enable fluid to exit thesecond chamber 616. A second exhaust valve 632 may be located within thesecond exhaust passage 630. The second exhaust valve 632 may be aone-way valve enabling fluid flow in a single direction, namely adirection away from the second chamber 616.

FIG. 7 shows the parallel vacuum pump 600 during a down stroke of thevacuum cycle. The down stroke may occur when a user puts weight on theprosthetic device during use. In alternative embodiments, the downstroke may occur when the piston is cycled using a power source. Asshown, the down stroke causes a volume of the second chamber 616 todecrease as a volume of the first chamber 614 increases. The fluid inthe second chamber 616 exits the second chamber 616 via the secondexhaust passage 630 in a direction D. The down stroke additionallycauses the volume of the first chamber 614 to increase. The firstchamber 614 pulls a fluid (e.g., air) from an evacuation volume, via thefirst intake passage 618 in a direction F.

FIG. 8 shows the parallel vacuum pump 600 during an up stroke of thevacuum cycle. The up stroke may occur when a user unloads weight on theprosthetic. This may occur when a user is walking or running. The springmember 656 causes a force that pulls on the vacuum pump and biases thepiston 606 upwards toward the top cap 610. In alternative embodiments,the up stroke may occur when the piston is cycled using an electricmotor. As shown, the up stroke causes a volume of the first chamber 614to decrease as a volume of the second chamber 616 increases. The fluidin the first chamber 614 exits the first chamber 614 via the firstexhaust passage 626 in a direction G. The up stroke additionally causesthe volume of the second chamber 616 to increase. The second chamber 616pulls a fluid (e.g., air) from an evacuation volume, via the secondintake passage 622, in a direction H.

FIG. 9 illustrates an example series vacuum pump 900. The series vacuumpump 900 comprises a housing 902 and a shaft 904. The shaft 904 moves inrelation to the housing 902. The housing 902 may include a cap 906 thatmay be coupled to the housing 902 via one of more clamps 908. Thehousing 902 and cap 906 may alternatively be screwed together via matingthreads, fastened together, adhered together, or otherwise coupled. Thecap 906 may additionally comprise a barb 910 and a connector 912 thatcouples the series vacuum pump 900 to a socket (e.g., socket 108 shownin FIG. 1). The connector 912 may provide a mechanical connectionbetween the series vacuum pump 900 and the socket. The barb 910 mayprovide a fluid connection between the series vacuum pump 900 and anevacuation volume (e.g., evacuation volume 204). The evacuation volumemay be formed between a socket and a liner that is mounted to a residuallimb positioned in the socket.

A first bearing 914 and a second bearing 916 provide an interfacebetween the housing 902 and the shaft 904. The first bearing 914 andsecond bearing 916 may provide support between the shaft 904 and housing902 as the shaft 904 and the housing 902 move in relation to each other.The bearings 914, 916 may maintain a working distance between an innerwall 918 of the housing 902 and an outer wall 920 of the shaft 904.

The shaft 904 may comprise a multi-piece assembly. For example, theshaft 904 may be an assembly comprising a body 922, a top cap 924, and abottom cap 926. The top cap 924 and bottom cap 926 may be coupled to aninternal wall 928 of the body 922. The bottom cap 926 may be tight-fit,screwed, adhered, or otherwise coupled to the body 922. In someembodiments, the bottom cap 926 may rest on a lip 930 on the internalwall 928 of the body 922. The top cap 924 may be coupled to a top of thebody 922 of the shaft 904. The top cap 924, bottom cap 926, and body 922may form a sealed volume 932 (e.g., sealed volume, 206).

A piston 934 is positioned in the sealed volume 932 and may form twoevacuation chambers within the sealed volume 932. For example, thepiston 934 may be movably situated in the sealed volume 932 and mayfluidly separate the sealed volume 932 into a first evacuation chamber936 and a second evacuation chamber 938. A compressible seal 940 may belocated on an outer diameter 942 of the piston 934. The compressibleseal 940 may fluidly separate the first evacuation chamber 936 and thesecond evacuation chamber 938 while enabling the piston 934 toreciprocate inside the shaft 904.

The piston 934 is coupled to the cap 906. For example, the piston 934may be threadably engaged with the cap 906 at a top portion 944 of thepiston 934. In some embodiments, the top portion 944 of the piston 934may connect to a cylinder 946 of the cap 906. In other embodiments, thetop portion 944 of the piston 934 may extend through an opening of thetop cap 924. In some embodiments, the joint may incorporate acompressible seal 948. The compressible seal 948 may maintain the sealedvolume 932 by preventing bleed through the joint between top portion 944and cylinder 946.

A bottom portion 950 of the piston 934 may pass through an opening 952in the bottom cap 926. The opening 952 may incorporate a compressibleseal 954, which may maintain the sealed volume 932 while enabling thebottom portion 950 of the piston 934 to pass through the opening 952.The bottom portion 950 of the piston 934 may be coupled to or abutting aspring element 956. The spring element 956 may be fairly rigid but actas a spring or dampening feature to the prosthetic. The spring element956 may have a spring rate within a range of about 10 N/mm and about 350N/mm. A bottom 958 of the spring element 956 may be coupled to fixturebottom cup 960.

The bottom cup 960 may keep the spring element 956 within the shaft 904.The prosthetic shaft may extend into an opening 962 in the body 922 ofthe shaft 904 and be coupled to the bottom of the shaft 904. Theprosthetic shaft may be screwed, threaded, tight-fit, clamped, adhered,or otherwise attached thereto. In some embodiments, the prosthetic shaftand the series vacuum pump 900 may be easily separable for multiplereasons. For example, a user may utilize different prosthesis dependingon activity. Alternatively, ease of separation may enable ease ofmaintenance and care for the series vacuum pump 900.

The piston 934, housing 902, and cap 906 may move in unison as anassembly in relation to the shaft 904 and top and bottom caps 924, 926.As the piston 934 moves within the sealed volume 932, the respectivevolumes of the first evacuation chamber 936 and the second evacuationchamber 938 vary. As the piston 934 moves in a direction A relative tothe sealed volume 932, the volume of the first evacuation chamber 936reduces and the volume of the second evacuation chamber 938 increases.As the piston 934 reciprocates and moves in a direction B relative tothe sealed volume 932, the volumes of the first evacuation chamber 936and second evacuation chamber 938 may again change, with the volume ofthe first evacuation chamber 936 increasing and the volume of the secondevacuation chamber 938 decreasing. In one embodiment, the piston 934 maybe powered by an electrical motor (not shown). In another embodiment, ifthe prosthesis is a prosthetic leg, the piston 934 may move down indirection B relative to the sealed volume 932 when a person puts weighton the prosthesis. When the person takes a step and the weight isreleased, the piston 934 may move upward in direction A relative to thesealed volume 932.

In this instance, the series vacuum pump 900 is a series pump, meaningthe second evacuation chamber 938 pulls a fluid from the evacuationvolume and the first evacuation chamber 936 pulls fluid from the secondevacuation chamber 938. The fluid may travel through one or morepassages which may incorporate one or more one-way valves. The valvesmay enable fluid to only flow in a single direction.

For example, an intake passage 964 fluidly connects the secondevacuation chamber 938 with the socket via barb 910. The intake passage964 includes an intake valve 966. The intake valve 966 is a one-wayvalve that enables fluid to only flow from the evacuation volume intothe second evacuation chamber 938. The second evacuation chamber 938pulls fluid from the evacuation volume via the intake passage 964 indirection J as the piston 934 travels upward in the direction B.

As the piston 934 travels upward, a volume of the first evacuationchamber 936 is reduced. As the volume of the first evacuation chamber936 is reduced, fluid from the first evacuation chamber 936 exits via anexhaust passage 972 in a direction K. The exhaust passage 972 may havean exhaust valve 974 that may enable single direction fluid flow. Forexample, the exhaust valve 974 may enable fluid to only flow in thedirection K.

As the piston 934 reciprocates and travels downward in the direction B,the volumes of the first evacuation chamber 936 and the secondevacuation chamber 938 change. As the volume of the second evacuationchamber 938 decreases, fluid travels from the second evacuation chamber938 into the first evacuation chamber 936 via a connector passage 968along a portion of the path labeled L. The connector passage 968 mayinclude a connector valve 970 which may enable fluid flow in path L. Airfrom the second evacuation chamber 938 may also exhaust from the secondevacuation chamber 938 via a one-way valve 977 along path V toatmosphere. The series vacuum pump 900 with the arrangement shown inFIG. 9 will act to generate a higher pressure differential between theevacuation volume and atmosphere than a parallel pump configuration.

FIG. 10 may be a cross-sectional view of an exemplary vacuum pump 1000that is a combination parallel and series pump. The vacuum pump 1000 mayincorporate similar features of the vacuum pump 300, 900 described withreference to FIGS. 3A-3C and 9. For example, a piston 1006 may belocated within a sealed volume formed within the shaft 1002. A cap 1028may be clamped, or otherwise removably affixed to a housing 1004.

The sealed volume may be formed by the shaft 1002, a top cap 1010, and abottom cap 1012. The piston 1006 may separate the sealed volume into afirst series chamber 1014 and a parallel chamber 1016. In thisembodiment, the piston 1006 may be a one-piece piston that incorporatesone or more intake valves. In other embodiments, the piston 1006 maycomprise a two-piece design as described with reference to FIGS. 5A-5D.In either design, the piston 1006 may incorporate passages fluidlyconnecting various chambers. For example, the piston 1006 may include aparallel intake passage 1018 that fluidly connects the parallel chamber1016 to an evacuation volume (e.g., evacuation volume 204/224 via barb1017). The parallel intake passage 1018 may include a parallel intakevalve 1020 that may be a one-way fluid valve enabling fluid flow in asingle direction M. As the piston travels upward in the direction Brelative to sealed volume 1033, the volume of the parallel chamber 1016may increase as it pulls fluid from the evacuation volume along the pathin the direction M.

As the volume of parallel chamber 1016 increases, the volume of thefirst series chamber 1014 decreases. As the piston 1006 travels upwardin a direction A relative to sealed volume 1033, the fluid in the firstseries chamber 1014 exhausts into a second series chamber 1022 via aconnection passage 1024 in a direction N. The connection passage 1024includes a connection valve 1026 that enables one-way fluid flowindicated in the direction N. The second series chamber 1022 may beformed between the cap 1028 and the shaft 1002. The cap 1028 and theshaft 1002 may form a second sealed volume as the second series chamber1022. As the piston 1006 travels upward in direction A relative tosealed volume 1033, the fluid in the first series chamber 1014 is pushedinto the second series chamber 1022 via connection passage 1024. As thisfluid is pushed into the second series chamber 1022, a pressure insidethe second series chamber 1022 increases as this fluid merges with fluidexisting within the second series chamber 1022. The increase in pressurein the second series chamber 1022 forces fluid to exhaust the secondseries chamber 1022 via a first exhaust passage 1030 in a direction O.The first exhaust passage 1030 may include an first exhaust valve 1032is pushed into atmosphere. The first exhaust valve 1032 may enable fluidflow in a single direction O.

The piston 1006 then reciprocates within the sealed volume 1033 andtravels downward in a direction B relative to sealed volume 1033. As thepiston 1006 moves downward, the volume of the parallel chamber 1016decreases and the volume of the first series chamber 1014 increases. Thefirst series chamber 1014 pulls fluid from the evacuation volume via aseries intake passage 1034. The fluid may travel through the seriesintake passage 1034 in a direction P. The series intake passage 1034 mayinclude a series intake valve 1036. The series intake valve 1036 mayenable one-way fluid flow in a direction P. At the same time, as thepiston 1006 travels downward in a direction B, the fluid located withinthe parallel chamber 1016 may exit the parallel chamber 1016 via theparallel exhaust passage 1038. The fluid may travel through the parallelexhaust passage 1038 past a parallel exhaust valve 1040 within theparallel exhaust passage 1038 and into atmosphere in a direction Q.

The combination series and parallel vacuum pump 1000 may realize thebenefits of both a series vacuum pump and a parallel vacuum pump. Thus,the combination vacuum pump 1000 may quickly achieve a strong vacuumcondition. The first series chamber 1014 and the parallel chamber 1016may act as a parallel vacuum pump and may exhaust fluid from theevacuation volume as both chambers 1014, 1016 pull air from the sameevacuation volume. At the same time, the first series chamber 1014 andthe second series chamber 1022 may act in concert to achieve a higherpressure differential in the evacuation volume.

FIG. 11 is an example of a multiple state series vacuum pump 1100. Themultiple stage series vacuum pump 1100 is similar to the combinationseries and parallel vacuum pump 1000 described with reference to FIG.10. For example, the series vacuum pump 1100 includes a housing 1102 anda shaft 1104. The housing 1102 and the shaft 1104 may be separated by afirst bearing 1106 and a second bearing 1108.

A top cap 1110 and bottom cap 1112 are coupled to the shaft 1104 andform a sealed volume. A piston 1116 may be situated in the sealed volumeand may separate the sealed volume into two separate sealed volumechambers. A third sealed volume chamber may be formed between the topcap 1110 and a cap 1114 coupled to the housing 1102. The three volumesare a first chamber 1118, a second chamber 1120, and a third chamber1122.

The first chamber 1118 is fluidly connected to an evacuation volume viaan intake passage 1124. An intake valve 1126 is located in line with theintake passage 1124. The intake valve 1126 may be a one-way valveenabling fluid flow in a single direction. Fluid may travel from theevacuation volume into the first chamber 1118 via the intake passage1124 in a direction R. Fluid in the first chamber 1118 may exit thefirst chamber 1118 and enter the second chamber 1120 via a firstconnection passage 1128 in a direction S. Fluid in the second chamber1120 may exit the second chamber 1120 and enter the third chamber 1122via a second connection passage 1132 in a direction T. Fluid in thethird chamber 1122 may exit into atmosphere via an exhaust passage 1136in direction U. Each of the passages may have a one-way valve thatenables fluid to flow in a single direction. The first connectionpassage 1128 may have a first connection valve 1130 and the secondconnection passage may have the second connection valve 1134. Theexhaust passage 1136 may have an exhaust valve 1138.

Movement of the piston 1116 may cycle the series vacuum pump 1100 andgenerate a vacuum condition in the evacuation volume. For example, asthe piston 1116 moves upward in a direction A, fluid is pulled from theevacuation volume into the first chamber 1118 via the intake passage1124 in a direction R. This movement causes fluid in the second chamber1120 to exit the second chamber 1120 and enter the third chamber 1122via first connection passage 1128 in direction S. This may causepressure in the third chamber 1122 to increase. As the pressureincreases, fluid may exit the third chamber 1122 into atmosphere via theexhaust passage 1136 in direction U. As the piston 1116 continues tocycle and move downward in a direction B, the volume of the firstchamber 1118 decreases and the fluid in the first chamber 1118 is forcedthrough the first connection passage 1128 into the increased volume ofthe second chamber 1120. The process then continues and the piston 116travels upward again in the sealed volume.

The multiple stage series vacuum pump 1100 supercharges the vacuum andforces a little extra air into each chamber. This in turn increases thepressure differential in the evacuation volume. As a result, an evenhigher vacuum condition is achieved in the evacuation volume. The highervacuum condition may result in better retention of the prosthetic to aresidual limb.

FIGS. 12A and 12B illustrate example schematics of a vacuum pump 1200that is switchable between a parallel configuration and a seriesconfiguration. In a switchable embodiment, the vacuum pump 1200 may beconfigured to operate in either a parallel configuration or a seriesconfiguration. A switch 1202 of the vacuum pump 1200 may be operable tofacilitate the change between the series operation and the paralleloperation.

FIGS. 12A and 12B include schematics of the vacuum pump 1200, the switch1202 and an evacuation volume 1204. As mentioned previously, theevacuation volume 1204 may be situated between a residual limb and asocket (e.g., residual limb 104 and socket 108 shown in FIG. 1). In someembodiments, the residual limb may be fitted with a sock or a liner. Aperson may fit a residual limb with a sock or a liner prior to insertingthe residual limb into a socket.

FIG. 12A is an example schematic of the switch 1202 in a parallelconfiguration. The vacuum pump 1200 may comprise a sealed volume 1206.The sealed volume 1206 may be separated into a first sealed volumechamber 1208 and a second sealed volume chamber 1210 by a piston 1212that is located within the sealed volume 1206. As the piston 1212reciprocates within the sealed volume 1206, a volume of the firstchamber 1208 and a volume of the second chamber 1210 may vary.

The switch 1202 may be fluidly coupled to the evacuation volume 1204 viaa parallel evacuation passage 1214. The parallel evacuation passage 1214may enter the switch and split into two different passages: a firstintake passage 1216 and a second intake passage 1218. The first intakepassage 1216 may fluidly connect the first chamber 1208 to theevacuation volume 1204 when the switch 1202 in operating in parallelmode. Additionally, while the switch 1202 is in parallel mode, thesecond intake passage 1218 may fluidly couple the second chamber 1210 tothe evacuation volume 1204.

The switch 1202 made additionally enable the first and second chambers1208, 1210 to exhaust a fluid from the respective chambers via aparallel exhaust passage 1220. For example, a first exhaust passage 1222may fluidly couple the first chamber 1208 to the parallel exhaustpassage 1220. A second exhaust passage 1224 may fluidly couple thesecond chamber 1210 to the parallel exhaust passage 1220.

As the piston 1212 travels downward in a direction B, the volume of thefirst chamber 1208 increases and the volume of the second chamber 1210decreases. As the volume of the first chamber 1208 increases, fluid ispulled from the evacuation volume 1204 via the parallel evacuationpassage 1214 and first intake passage 1216. As the volume of the secondchamber 1210 decreases, fluid is pushed from the second chamber 1210into the second exhaust passage 1224 and parallel exhaust passage 1220and then into atmosphere.

As the piston 1212 reciprocates and travels upward in a direction A, thevolume of the second chamber 1210 increases and the volume of the firstchamber 1208 decreases. As the volume of the second chamber 1210increases, the second chamber 1210 pulls fluid from the evacuationvolume 1204 via the parallel evacuation passage 1214 and second intakepassage 1218. Likewise, as the volume of the first chamber 1208decreases, the fluid in the first chamber 1208 is pushed into the firstexhaust passage 1222 and into the parallel exhaust passage 1220.

FIG. 12B is an example schematic of the switch 1202 in a seriesconfiguration. In a series configuration, the switch 1202 may be fluidlycoupled to the evacuation volume 1204 via an series evacuation passage1226. The series evacuation passage 1226 may enter the switch 1202 andfluidly coupled to a chamber intake passage 1228. The chamber intakepassage 1228 may fluidly connect the first chamber 1208 to the seriesevacuation passage 1226.

A first series connection passage 1230 may fluidly couple the firstchamber 1208 to a series switch connection passage 1231 in the switch1202. The switch connection passage 1231 may be fluidly connected to thesecond series connection passage 1232, which may be fluidly coupled tothe second chamber 1210. The second chamber 1210 may exhaust a fluid viaa series exhaust passage 1236. The series exhaust passage 1236 may befluidly coupled to a series switch exhaust passage 1238. The seriesswitch exhaust passage 1238 may be fluidly coupled to the second chamber1210 to atmosphere.

FIG. 13A is a perspective view of a switchable series/parallel vacuumpump 1300. FIG. 13C is a partial cutaway view of the switchable vacuumpump 1300 along line 13C-13C in FIG. 13B. FIG. 13B shows a side view ofthe switch 1302 situated between an upper housing 1304 and a lowerhousing 1306. A fluid connector 1316 may fluidly couple the switch 1302to an evacuation volume.

The cross-sectional view in FIG. 13C shows the interplay of the switch1302 with a first chamber 1310 and a second chamber 1312. FIG. 13C alsoincludes a cross-sectional view of a shaft 1308 within upper housing1304 and lower housing 1306 and a piston 1314. A first exhaust passage1318 may fluidly couple the first chamber 1310 to the switch 1302. Asecond exhaust passage 1320 may fluidly couple the second chamber 1312to the switch 1302. The first and second exhaust passages 1318, 1320 mayrespectively include a first exhaust valve 1322 and a second exhaustvalve 1324. The exhaust valves 1322, 1324 may be one-way valves enablingfluid to only flow in a single direction out of the respective chambers1310, 1312. More disclosure regarding the function of a housing 1304,1306, shaft 1308, and piston 1314 compatible with the switch 1302 isprovided in U.S. Pat. No. 7,744,653, the entire disclosure of which ishereby incorporated by reference.

The exhaust valves 1322, 1324 may be incorporated into either the upperhousing 1304 (see FIGS. 13C and 14) or a switch housing 1326. A spool1328 may be situated within the switch housing 1326. The spool 1328 mayfacilitate switching the switchable vacuum pump 1300 between seriesoperation and parallel operation. An exploded version of the switch 1302is shown in FIG. 14. FIG. 14 shows the switchable vacuum pump 1300 withan upper housing 1304 and a lower housing 1306.

The switch 1302 may include the switch housing 1326. The switch housing1326 may include a fluid connector 1316. The fluid connector 1316 mayfluidly couple the switchable vacuum pump 1300 to an evacuation volume.The switch housing 1326 may include the first and second exhaust valve1322, 1324. In some embodiments the switch housing 1326 may additionallyinclude a first intake valve 1400 and a second intake valve 1402. Thespool 1328 may be insertable into an opening 1404 in the switch housing1326. A spring 1406 may be inserted into the opening 1404 first and maywork to move the spool 1328 between a series position and a parallelposition. One or more set screws 1408 may or other fasteners may affixthe switch 1302 to the switchable vacuum pump 1300.

FIG. 15 is a side view of the switch 1302. FIGS. 16A and 16B arecross-sectional views of the switch 1302 taken through section lines16A-16A in FIG. 15, and FIG. 16C is a cross-sectional view of the switch1302 taken through section lines 16C-16C in FIG. 15.

FIG. 16A is a cross-sectional view of the switch 1302 in parallel mode.The switch 1302 may have an automatic function that changes the positionof a spool 1608 in the switch 1302 between the position shown in FIG.16A and the position shown in FIG. 16B. The switch 1302 may include aswitch housing 1602. The switch housing 1602 may comprise a series ofopenings, apertures, and valves. A fluid connector 1604 may be coupledto an opening 1606 in the switch housing 1602. The fluid connector 1604may provide a connection point to fluidly couple the switch 1302 to anevacuation volume. A spool 1608 may be situated in an opening 1610 ofthe switch housing 1602.

The spool 1608 may comprise a series of grooves on its outer diametersurface. The series of grooves may incorporate fluid passages enablingair flow between an evacuation volume and a vacuum pump. For example aspace between the spool 1608 and the opening 1610 may form a centralintake passage 1612. The central intake passage 1612 may be fluidlycoupled to a first intake passage 1614 and a second intake passage 1616.The first intake passage 1614 may be fluidly coupled to a first chamberof a vacuum pump (e.g., first chamber 208, 336 as shown in FIGS. 2 and3C) and second intake passage 1616 may be fluidly coupled to a secondchamber (e.g., second chamber 210, 338 as shown in FIGS. 2 and 3C). Thefirst intake passage 1614 and the second intake passage 1616 may includea first intake valve 1618 and a second intake valve 1620, respectively.Thus, air passing into the central intake passage 1612 may besimultaneously provided to both intake valves 1618, 1620 when the spool1608 is in the position shown in FIG. 16A. Thus, the first and secondchambers may be filled directly from the evacuation volume as is done ina parallel pump.

A second rectangular groove in the spool 1608 and the inner wall of theopening 1610 around it may comprise a central exhaust passage 1622. Thecentral exhaust passage 1622 may be coupled to a first exhaust passage1624 and a second exhaust passage 1626. The first exhaust passage 1624and second exhaust passage 1626 may be fluidly coupled to a firstchamber and second chamber of the vacuum pump, respectively. The firstand second exhaust passages 1624, 1626 may incorporate a first andsecond exhaust valve 1628, 1630, respectively. Thus, air from the firstand second chambers may be simultaneously vented through the secondexhaust passage 1626 via the exhaust valves 1628, 1630.

When the spool 1608 is in the position shown in FIG. 16B, air may beprovided to the first chamber of the pump via the first intake passage1614 and the first intake valve 1618. The second intake valve 1620 iscut off from the central intake passage 1612 due to the shifted positionof the spool 1608. Instead, the second intake valve 1620 receives airfrom the central exhaust passage 1622 that links the first exhaust valve1628 (which is connected to the first chamber of the pump) to the secondintake valve 1620. Air may then exhaust from the second chamber of thepump via the second exhaust valve 1630 and second exhaust passage 1626.Accordingly, the configuration shown in FIG. 16B illustrates the switch1302 setting the vacuum pump to work as a series pump.

One end of the spool 1608 may accept a spring 1636 in a switch volume1638. The switch volume 1638 may comprise a sealed volume. As shown inFIG. 16C, the switch volume 1638 may have its air pressure synchronizedwith the pressure in the evacuation volume via a spring passage 1640.The spring passage 1640 is connected to the first intake passage 1614which is also in fluid communication with the first intake valve 1618.The pressure in the switch volume 1638 may control a position of thespool 1608. For example, the spool may be in the first position shown inFIG. 16A. When a sufficient vacuum condition is achieved in theevacuation volume (and accordingly also in the switch volume 1638), thespring 1636 may compress, as shown in FIGS. 16B and 16C, due to thepressure dropping in the spring passage 1640 and switch volume 1638. Thespring 1636 may automatically compress as adequate vacuum is achieved,thereby causing the spool 1608 to move from the parallel mode of FIG.16A to the series mode of FIG. 16B.

As mentioned previously herein, the parallel mode of the vacuum pumpreduces pressure more quickly than the series mode by more quicklyevacuating the evacuation volume. However, the series mode of the pumpcan produce a lower pressure than the parallel mode, and a lowerpressure may provide a stronger connection between the prosthetic deviceand a residual limb. Thus, it is desirable to use parallel mode toreduce pressure quickly and then switch to series mode to deepen andstrengthen the vacuum after a certain vacuum condition is reached usingparallel mode. The user may not wish to have to switch manually betweenthe two modes. The automatic switch 1700 may remove ambiguity in when toswitch the pump and not rely on the user remembering to manually switchthe pump to achieve optimal vacuum conditions.

FIG. 17A is a cross-sectional view of a manual switch 1700 arranged in aparallel mode. The manual switch 1700 includes a switch housing 1702.The switch housing 1702 may comprise a series of openings and apertures.A fluid connector 1704 may be coupled to an opening 1706 in the switchhousing 1702. The fluid connector 1704 may provide a connection point tofluidly couple the manual switch 1700 to an evacuation volume. A spool1708 may be situated and slidable within an opening 1712 of the switchhousing 1702.

The spool 1708 may comprise a series of grooves 1722, 1736 on its outersurface. The series of grooves may, in conjunction with the inner wallsof the opening 1712, form fluid passages enabling air flow between anevacuation volume and a vacuum pump. For example, a first section mayact as an intake passage 1736. The intake passage 1736 may be fluidlycoupled to a first intake passage 1714 and a second intake passage 1716.The first intake passage 1714 may be fluidly coupled to a first chamberof a vacuum pump (e.g., first chamber 208, 336 shown in FIGS. 2 and 3C)and second intake passage 1716 may be fluidly coupled to a secondchamber of the vacuum pump (e.g., second chamber 210, 338 as shown inFIGS. 2 and 3C). The first intake passage 1714 and the second intakepassage 1716 may include a first intake valve 1718 and a second intakevalve 1720, respectively. Thus, the intake passage 1736 maysimultaneously provide air to the first and second chambers of a vacuumpump from the fluid connector 1704.

A second groove in the spool 1708 may, in conjunction with the innerwalls of the opening 1712, comprise an evacuation exhaust passage 1722.The evacuation exhaust passage 1722 may couple to a first exhaustpassage 1724 and a second exhaust passage 1726. The first exhaustpassage 1724 and second exhaust passage 1726 may be fluidly coupled to afirst chamber and second chamber of the vacuum pump, respectively. Thefirst and second exhaust passages 1724, 1726 may incorporate a first andsecond exhaust valve 1728, 1730, respectively. Thus, the evacuationexhaust passage 1722 may simultaneously receive exhaust air from thefirst and second chambers of the vacuum pump and allow the air to exitthrough the second exhaust passage 1726.

Each end of the spool 1708 may include a button, stem, or other controlmember. For example, a first side of the spool 1708 may incorporate afirst button 1732 and the second side of the spool 1708 may incorporatea second button 1734. The buttons 1732, 1734 may enable user to engageand longitudinally slide the spool 1708 relative to the opening 1712between a parallel position (as shown in FIG. 17A) and a series position(as shown in FIG. 17B).

In FIG. 17B, the spool 1708 is arranged in a series mode. For example,the spool 1708 is positioned such that the intake passage 1736 mayreceive air from the fluid connector 1704 and provide air into one ofthe chambers of the vacuum pump via first intake valve 1718. Air cannotpass directly from the fluid connector 1704 into the second intake valve1720. However, the exhaust passage 1722 is positioned relative to thesecond intake valve 1720 and the first exhaust valve 1728 so that airfrom the first chamber (via the first exhaust valve 1728) may beprovided into the second chamber (via the second intake valve 1720). Airin the second chamber may then exhaust via the second exhaust valve1730. Accordingly, the manual switch 1700 causes the pump (e.g., pump1300) to operate as a parallel vacuum pump with the spool 1708 in theposition of FIG. 17A and to operate as a series vacuum pump with thespool 1708 in the position of FIG. 17B.

As explained above, a user may switch the vacuum pump between theparallel and series modes during use of a prosthetic device to reach acertain vacuum condition quickly and then to deepen that vacuum. Themanual switch 1700 of FIGS. 17A-17B allows the user to manually decidewhen to change from parallel mode to series mode. The two modes mayprovide a user with greater control over the vacuum condition in theprosthetic device and may therefore enhance its comfort andcustomizability.

Various inventions have been described herein with reference to certainspecific embodiments and examples. However, they will be recognized bythose skilled in the art that many variations are possible withoutdeparting from the scope and spirit of the inventions disclosed herein,in that those inventions set forth in the claims below are intended tocover all variations and modifications of the inventions disclosedwithout departing from the spirit of the inventions. The terms“including:” and “having” come as used in the specification and claimsshall have the same meaning as the term “comprising.”

What is claimed is:
 1. A vacuum pump for a prosthetic device, comprising: a housing having an inner wall; a piston having an outer diameter and being secured within the housing; a shaft having an inner surface and being positioned between the inner wall of the housing and the outer diameter of the piston; an upper fluid chamber positioned between a top surface of the piston and the inner surface of the shaft, the upper fluid chamber having a variable volume as the shaft moves axially in relation to the piston and the housing, the upper fluid chamber being fluidly connected to a socket of the prosthetic device through a first valve and fluidly connected to atmosphere through a second valve; a lower fluid chamber positioned between a bottom surface of the piston and the inner surface of the shaft, the lower fluid chamber having a variable volume as the shaft moves axially in relation to the piston and the housing, the lower fluid chamber being fluidly connected to the socket through a third valve and fluidly connected to atmosphere through a fourth valve.
 2. The vacuum pump of claim 1, wherein the first valve and third valve are independently fluidly connectable to an evacuation volume.
 3. The vacuum pump of claim 2, wherein the evacuation volume decreases as the vacuum pump operates causing a vacuum condition in the evacuation volume.
 4. The vacuum pump of claim 1, wherein the shaft is axially movable to compress a volume of the upper fluid chamber while expanding a volume of the lower fluid chamber and vice versa.
 5. The vacuum pump of claim 1, wherein compressing a volume of the upper fluid chamber causes air to exhaust via the second valve into atmosphere.
 6. The vacuum pump of claim 1, wherein the piston is an assembly comprising: a first piece of the piston, the first piece of the piston being substantially cylindrically shaped; a second piece of the piston, the second piece of the piston being a flattened torus.
 7. The vacuum pump of claim 6, wherein the first piece of the piston incorporates a series of fluid channels fluidly connecting the upper fluid chamber and the lower fluid chamber to the socket.
 8. The vacuum pump of claim 1, further comprising: a compressible seal positioned around an outer diameter of the piston, wherein the compressible seal fluidly separates the upper fluid chamber from the lower fluid chamber while enabling the shaft to move axially in relation to the piston.
 9. The vacuum pump of claim 1, wherein the valves are one-way valves allowing fluid flow in a single direction.
 10. The vacuum pump of claim 1, further comprising a prosthetic leg, the prosthetic leg comprising a prosthetic foot and a socket, the socket being configured to accept a residual limb, the vacuum pump being configured to evacuate fluid from the socket.
 11. A vacuum pump for a prosthetic device, comprising: a housing having an inner wall; a piston having an outer diameter and being secured within the housing; a shaft having an inner surface and being positioned between the inner wall of the housing and the outer diameter of the piston; an upper fluid chamber positioned between a top surface of the piston and the inner surface of the shaft, the upper fluid chamber having a variable volume as the shaft moves axially in relation to the piston and the housing, the upper fluid chamber being fluidly connected to a first pair of one-way valves; a lower fluid chamber positioned between a bottom surface of the piston and the inner surface of the shaft, the lower fluid chamber having a variable volume as the shaft moves axially in relation to the piston and the housing, the lower fluid chamber being fluidly connected to a second pair of one-way valves.
 12. The vacuum pump of claim 11, wherein at least a first valve of the first and second pair of one-way valves is fluidly connected to a socket of the prosthetic device and wherein at least a second valve of the first and second pair of one-way valves is fluidly connected to atmosphere.
 13. The vacuum pump of claim 11, wherein compressing a volume of the upper fluid chamber causes air to exhaust via the one of the first pair of one-way valves into atmosphere.
 14. The vacuum pump of claim 11, further comprising: a compressible seal positioned around an outer diameter of the piston, wherein the compressible seal fluidly separates the upper fluid chamber from the lower fluid chamber while enabling the shaft to move axially in relation to the piston.
 15. A vacuum pump for a prosthetic device, the vacuum pump comprising: a shaft; a housing; a first fluid chamber, a second fluid chamber, and a third fluid chamber, each of the first, second, and third fluid chambers being sealed and having a variable volume upon movement of the shaft relative to the housing; wherein the first fluid chamber is fluidly connected to a first pair of one-way valves, the second fluid chamber is fluidly connected to a second pair of one-way valves, and the third fluid chamber is fluidly connected to a third pair of one-way valves.
 16. The vacuum pump of claim 15, wherein at least one of the one-way valves is shared by the first pair of one-way valves and the second pair of one-way valves.
 17. The vacuum pump of claim 15, wherein the first and second fluid chambers are arranged in series.
 18. The vacuum pump of claim 15, wherein the first and third fluid chambers are arranged in parallel.
 19. A vacuum pump for a prosthetic device, the vacuum pump comprising: a housing having an inner wall; a piston having an outer diameter, a top surface, and a bottom surface, the piston being held stationary relative to the housing; a shaft having an inner surface and being positioned between the inner wall of the housing and the outer diameter of the piston; an upper fluid chamber positioned between the top surface of the piston and the inner surface of the shaft, the upper fluid chamber having a variable volume as the shaft moves axially in relation to the piston and the housing, the upper fluid chamber being in fluid communication with a first valve and a second valve; a lower fluid chamber positioned between the bottom surface of the piston and the inner surface of the shaft, the lower fluid chamber having a variable volume as the shaft moves axially in relation to the piston and the housing, the lower fluid chamber being in fluid communication with a third valve and a fourth valve; a switch configured to control the operation of the vacuum pump between a parallel vacuum pump configuration and a series vacuum pump configuration; wherein at least one of the first and third valves are fluidly connected to the a socket of the prosthetic device and at least one of the second and forth valve is fluidly connected to atmosphere.
 20. The vacuum pump of claim 16, wherein in the parallel vacuum pump configuration, the first and third valves are both fluidly connected to the socket and the second and fourth valves are fluidly connected to atmosphere, and wherein in the series vacuum pump configuration, the first valve is fluidly connected to the socket, the second valve is fluidly connected to the lower fluid chamber, the third valve is fluidly connected to the lower fluid chamber, and the fourth valve is fluidly connected to atmosphere.
 21. A method of operating a vacuum pump for a prosthetic device, the method comprising: providing a vacuum pump, the vacuum pump comprising: a housing having an inner wall; a piston having an outer diameter and being secured within the housing; a shaft having an inner surface and being positioned between the inner wall of the housing and the outer diameter of the piston; an upper fluid chamber positioned between a top surface of the piston and the inner surface of the shaft, the upper fluid chamber having a variable volume as the shaft moves axially in relation to the piston and the housing, the upper fluid chamber being fluidly connected to a socket of the prosthetic device through a first valve and fluidly connected to atmosphere through a second valve; a lower fluid chamber positioned between a bottom surface of the piston and the inner surface of the shaft, the lower fluid chamber having a variable volume as the shaft moves axially in relation to the piston and the housing, the lower fluid chamber being fluidly connected to the socket through a third valve and fluidly connected to atmosphere through a fourth valve; attaching the vacuum pump to the socket, the socket being configured to accept a liner over a residual limb; moving the shaft in a first axial direction relative to the piston causing air to exhaust from the upper fluid chamber through the second valve and air to be drawn into the lower fluid chamber through the third valve; and moving the shaft in a second axial direction relative to the piston causes air to exhaust from the lower fluid chamber through the fourth valve and air to be drawn into the upper fluid chamber through the first valve.
 22. The method of claim 21, further comprising: generating a vacuum condition between the socket and the liner when air is drawn into the lower fluid chamber through the third valve.
 23. The method of claim 21, further comprising: connecting the vacuum pump to a prosthetic foot; transferring load from the socket to the prosthetic foot through the vacuum pump.
 24. The method of claim 21, further comprising: increasing a fluid volume of the lower fluid chamber as the shaft moves axially in the first axial direction; and decreasing a fluid volume of the upper fluid chamber as the shaft moves axially in the first axial direction.
 25. A vacuum pump switch for a prosthetic device, comprising: a housing; an inlet passage formed in the housing and configured to provide fluid communication with an evacuation volume; a first fluid inlet valve passage configured to provide fluid communication to a first chamber of a vacuum pump; a second fluid inlet valve passage configured to provide fluid communication to a second chamber of the vacuum pump; a first fluid outlet valve passage configured to provide fluid communication to the first chamber; a second fluid outlet valve passage configured to provide fluid communication to the second chamber; an outlet passage formed in the housing; a switch, the switch being operable between a first position and a second position, wherein in the first position fluid flow from the inlet passage is provided simultaneously to the first and second fluid inlet valve passages and flow to the outlet passage is provided simultaneously from the first and second fluid outlet valve passages, and wherein in the second position fluid flow from the inlet passage is provided to the first fluid inlet valve passage, fluid flow to the second fluid inlet valve passage is provided from the first fluid outlet valve passage, and fluid flow to the outlet passage is provided from the second fluid outlet valve passage.
 26. The vacuum pump switch of claim 25, further comprising: a vacuum pump comprising a housing and a piston, the housing comprising a sealed volume, the piston dividing the sealed volume into the first chamber and the second chamber. 